Microorganisms, such as bacteria, are important for the production of a wide variety of useful bio-preparations. These microorganisms play crucial roles in, for example, the food industry, pharmaceuticals, agriculture, mining, oil production, environmental clean-up, and waste management.
The high demand for fossil fuels necessitates efficient production of oil. As oil wells mature, it becomes more difficult and costly to continue to pump oil at an economically viable rate. Therefore, there is a need to develop improved methods of oil recovery. One such mechanism utilizes microbes and their by-products.
Oil exists in small pores and narrow fissures within the body of reservoir rocks underneath the surface of the earth. Natural pressure of the reservoir causes the oil to flow up to the surface, thereby providing primary production; however as oil production progresses, the reservoir pressure is depleted to a point at which artificial lift or pumping is required to maintain an economical oil production rate.
When it is necessary to provide external energy for the reservoir to achieve additional oil recovery (secondary recovery), the extra energy can be introduced by injecting gas (gas injection) and/or water (water flooding). After some years of operation in a field, the injected fluids flow preferentially along high permeable layers that cause these fluids to by-pass oil saturated areas in the reservoir. Therefore, an increasing quantity of water (or gas) rises with the oil and, by decreasing the ratio of oil to water, eventually it becomes uneconomic to continue the process and the field must be abandoned. In this situation, a third stage of oil recovery, so-called tertiary production or Enhanced Oil Recovery (EOR) can be considered.
At this tertiary stage, technically advanced methods are employed to either modify the properties of reservoir fluids or the reservoir rock characteristics. In general, the methods can be classified into four main categories as thermal methods, chemical methods, miscible or solvent injection, and microbial methods.
Microbial Enhanced Oil Recovery (MEOR) is a multidisciplinary field incorporating, among others: geology, chemistry, microbiology, fluid mechanics, petroleum engineering, environmental engineering and chemical engineering. The microbial processes proceeding in MEOR can be classified according to the oil production problem in the field: well bore clean-up removes mud and other debris blocking the channels where oil flows; well stimulation improves the flow of oil from the drainage area into the well bore; and enhanced water floods increase microbial activity by injecting selected microbes and sometimes nutrients.
Thus, MEOR uses microorganisms and/or their metabolites to enhance the recovery of residual oil. In this method, nutrients and suitable bacteria, which preferably grow under the anaerobic reservoir conditions, are injected into the reservoir. Microbial by-products that can include biosurfactants, biopolymers, acids, solvents, gases, and enzymes modify the properties of the oil and the interactions between oil, water, and the porous media, thereby increasing the mobility, and consequently the recovery, of oil.
Microorganisms also play critical roles in agriculture. A plant's nutrition, growth, and proper functioning are dependent on the quantity and distribution of robust populations of natural microflora that in turn, are influenced by soil fertility, tillage, moisture, temperature, aeration, organic matter, and many other factors. Prolonged drought, variable rainfall, and other environmental variations, including the proliferation of nematodes and other pests, and weeds influence those factors and affect soil microflora diversity and plant health.
As synthetic contact pesticide chemistry and soil fumigants face greater scrutiny, and as new nematicide, herbicide, plant growth regulator, insecticide, bactericide, and fungicide and other crop input chemistry pipelines shrink due to increasing regulatory thresholds, sustainable biological pesticides, growth promoting microbes, microbes that increase the nutritional content of soils and help manage water use efficiency are becoming more important alternatives, particularly those that give similar levels of efficacy as the conventional pesticides, fumigants, plant growth regulators, surfactants and fertilizers.
Nematodes are pests known to infect plants and animals. These microscopic worms can be found in almost every type of environment. When residing in soil, nematodes feed on the roots of the plant, causing significant damage to the root structure and improper development of plants. The damage is generally manifested by the growth of galls, root knots, and other abnormalities. Gall formation leads to reduced root size and ineffectiveness of the root system, which in turn seriously affects other parts of the plant. As a result, the weakened plant becomes vulnerable to attacks by other pathogens. Without proper treatment, the plant dies. Nematodes cause millions of dollars of damage each year to turf grasses, ornamental plants, and food crops.
Chemical nematicides have been widely used to combat and control nematodes. These nematicides range from gas and liquid fumigation, such as methyl bromide and chloropicrin, to application of organophosphates and carbamates, such as thionazin and oxamyl. Despite the widespread use of chemical nematicide in controlling nematodes, there exist serious drawbacks of these methods. First, chemical nematicides exhibit low efficacy against nematodes, in particular, against final instar larvae. Second, they are highly toxic and can harm non-target organisms such as humans, domestic animals, beneficial insects, and wildlife. In addition, their residues may remain on the crop and accumulate in the soil, water, or air. Another concern is the development of resistance to pesticides by the targeted organisms.
Due to the disadvantages of chemical pesticides, the demand for safer pesticides and alternate pest control strategies is increasing. In recent years, biological control of nematodes has received considerable attention. This method utilizes biological agents such as live microbes, and bio-products derived from these microbes. These biological pesticides have important advantages over conventional pesticides. For example, they are less harmful compared to the conventional chemical pesticides. They are more efficient and specific. They often biodegrade quickly, leading to less environmental pollution.
Microbes and their by-products are useful in many settings in addition to oil production and agriculture. These other uses include, but are not limited to, in remediation of soils, water and other natural resources; mining; animal feed; waste treatment and disposal; food and beverage preparation and processing; and human health.
Interest in microbial surfactants has been steadily increasing in recent years due to their diversity, environmentally friendly nature, possibility of large-scale production, selectivity, performance under extreme conditions, and potential applications in environmental protection. Microbially produced surfactants, i.e., biosurfactants reduce the interfacial tension between water and oil and, therefore, a lower hydrostatic pressure is required to move the liquid entrapped in the pores to overcome the capillary effect. Secondly, biosurfactants contribute to the formation of micelles providing a physical mechanism to mobilize oil in a moving aqueous phase.
Biosurfactants enhance the emulsification of hydrocarbons, have the potential to solubilize hydrocarbon contaminants and increase their availability for microbial degradation. The use of chemicals for the treatment of a hydrocarbon polluted site may contaminate the environment with their by-products, whereas biological treatment may efficiently destroy pollutants, while being biodegradable themselves. Hence, biosurfactant-producing microorganisms may play an important role in the accelerated bioremediation of hydrocarbon-contaminated sites. These compounds can also be used in enhanced oil recovery as well as for other applications including herbicides and pesticides formulations, detergents, healthcare and cosmetics, pulp and paper, coal, textiles, ceramic processing and food industries, uranium ore-processing, and mechanical dewatering of peat.